1. Field of the Invention
The present invention is related to a method of handling cell reselection, and more particularly, to a method of handling cell reselection which ensures load balancing when communication devices in idle mode attempt to perform cell reselection.
2. Description of the Prior Art
The 3rd Generation Partnership Project (3GPP) has initiated the Long Term Evolution (LTE) program to bring novel network architecture and configuration, novel technology, and novel applications and services to provide reduced latency, improved spectral efficiency and faster user experiences with less cost.
Upon powered up or losing coverage, a communication device (i.e., a UE) of a communication system may search for suitable cells, such that the UE can receive communication services. If a suitable cell is found, the UE may registers with the cell when necessary. Furthermore, if the UE is in idle mode and not actively communicating with the cell, the UE may then camp on the cell and periodically search for better cells. When a better cell is found, the UE may select the better cell as a serving cell via a process commonly referred to as cell reselection. The searches performed in idle mode may allow the UE to camp on the best possible cell even if channel conditions change—for example, as the UE moves to a new location. In this way, the UE can reliably receive incoming paging messages and initiate or receive calls.
Basically, the UE selects a cell to camp on according to frequency priority as being in idle mode. Frequency priorities of different (inter) frequencies or inter radio access technology (inter-RAT) frequencies are determined according to CellReselectionPriority specified in 3rd Generation Partnership Project (3GPP) standard TS 36.331, which may be provided to the UE in a system information, in an RRCConnectionRelease message, or by inheriting from another RAT at inter-RAT cell (re) selection. And based on 3GPP standard TS 36.304, a frequency list or a cell list, which is associated with frequency priority, is configured at the time the UE goes to idle mode.
Therefore, existing cell reselection mechanisms may cause UEs in idle mode to concentrate on the cell with highest frequency priority, while it is beneficial if the UEs are distributed between the available frequencies in a way such that the capacity the communication system can offer is utilized in a good manner.
Obviously, there is a need for an improved method of handling cell reselection.